Bicruciate retaining (BCR) implants are known and have been in use since at least the early 1970s. Their use allows the preservation of both cruciate ligaments, the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Early designs included implants that were bicompartmental, i.e., the articular cartilage of the distal femur and the proximal tibia was replaced to alleviate pain and restore function, but not the patella and corresponding trochlear groove. However, starting in the late 1970s, the use of BCR implants started to decline as the introduction of the tricompartmental knees gained popularity.
There is a never ending quest to improve/restore natural knee kinematics following total knee replacement especially with the baby boomer generation getting surgery at a much younger age and still expecting a return to normal, active lifestyle activities such as golf, biking, hiking, and skiing. However, modern day implants still have limitations in offering natural joint kinematics. For example, a common misnomer in what the surgical community presently refers to as a Cruciate Retaining (CR) knee, the PCL is preserved but not the ACL. Therefore, the best that this knee can ever be is equivalent to an ACL deficient knee. In a Posterior Stabilized (PS) knee, both cruciates are sacrificed and only a partial function of the PCL is restored through the use of a cam on the femoral component and a post on the tibial insert. Therefore, since knees with compromised or torn cruciates are intrinsically unstable, it is believed that preserving both cruciates would improve joint stability and function following Total Knee Arthroplasty (TKA).
BCR implants may be indicated for use in situations which are similar to standard PCL-retaining TKA devices, or which are unique to BCR implants. For example, BCR indications for use which are similar to standard PCL-retaining devices may include painful, disabling joint disease of the knee resulting from non-inflammatory degenerative joint disease (including osteoarthritis, traumatic arthritis or avascular necrosis), rheumatoid arthritis or post-traumatic arthritis. Additional indications include post-traumatic loss of knee joint configuration and function; moderate varus, valgus, or flexion deformity in which the ligamentous structures can be returned to adequate function and stability; revisions of previous unsuccessful knee replacement or other procedure; fracture of the distal femur and/or proximal tibia that cannot be stabilized by standard fracture management techniques; and situations in which the PCL is intact, functional, and healthy. BCR implants may additionally be used in situations retaining the ACL for closer-to-natural stability, or even in situations with a deficient ACL.
Some drawbacks of prior art BCR baseplate designs are avulsion (tearing away) of the tibial eminence, and less than optimal instrumentation and surgical techniques, making surgery more challenging. Improved tibial implants and methods of implantation would thus be desirable.